Push-rod switches



Aug. 22, 1961 M. FRACHON PUSH-ROD SWITCHES Filed March 10. 1959 INVENTOR.

United States Patent 2,997,565 PUSH-ROD SWITCHES Marc Frachon, La Pierre Souveraine, Saint Genis Laval, France Filed Mar. 10, 1959, Ser. No. 798,419 Claims priority, application France Mar. '19, 1958 6 Claims. (Cl. 200-153) This invention refers to electric switches actuated by a slidable pusher rod such as those which are used in automatic machine tools, as for instance for limiting the stroke of a slidable carriage, for initiating another operation, etc. These switches general-1y comprise a substantially liquid-tight housing which carries the slidable pusher and the adjustment is eifected either by means of devices carried by the pusher-member, or merely by displacing the switch itself on its support.

This adjustment of the known switches is uneasy. The inner mechanism of the switch is generally intricate and expensive.

The present invention has for its object to provide an electric switch of the kind in question which will be very simple in construction, quite safe in operation and easily adjusted by means of an adjusting knob associated with a graduated dial without any kind of adjusting screw, nut or the like. In accordance with this invention in an electric switch actuated by a slidable pusher rod, the said pusher rod carries a cam surface which oscillates a micro-switch unit pivotal'ly supported by the frame of the apparatus, against biassing means which tend to return the said micro-switch unit towards a position for which its actuating button rests against an adjustable abutment which thus causes actuation of its inner contact mechanism.

It will be appreciated that when the cam surface disengages the micro-switch unit from the adjustable abutment, the button of the said micro-switch unit is released with respect to the unit itself, whereby the inner contact mechanism of the unit is actuated. Conversely when the cam surface permits the micro-switch unit to move towards the adjustable abutment under the action of the biassin-g means the button of the said unit is pushed with respect to the latter and therefore the inner contact mechanism of the unit is actuated in the reverse direction. The use of a. micro-switch unit ensures a snapping action, together with a high switching power. In accordance with the invention the adjustable abutment is preferably realized in the form of a spiral cam actuated by an outer knob which may thus rotate through almost one full revolution in front of an appropriate dial whereby an extremely precise adjustment may be effected even during operation of the switch.

In an embodiment the cam surface is easily removable from the pusher rod in such a manner that the latter may receive a pre-determined cam surface for each particular application. The cam surface may be prevented from rotating with the pusher rod, when the latter is cylindrical, by means of appropriate guides provided in the apparatus.

In the annexed drawings:

FIG. 1 is an elevation of a pusher-switch according to the invention.

FIG. 2 is a section thereof taken along line H-II of FIG. 3.

FIG. 3 is a transverse section taken along line III-III of FIG. 2.

The apparatus illustrated in the drawing comprises a switch case 1 having a front cover 2 secured in position by means of screws such as 3. A cylindrical pusher rod 4 is slidable through the rvertical lateral walls of this switch case 1, the said rod being urged towards the right in FIG. 2 by a spring 5 having one end attached onto a pin 6 carried by the rear wall of the switch case and the other one onto a pin 7 carried by the pusher rod itself. A sufiicient tightness against dust or moisture is ensured by an appropriate sealing device 8 secured against the outer side of the right lateral wall and by a blind socket 9 secured against the outer side of the opposed left lateral wall of the switch case.

The rear wall of the switch case carries a pin 10 on which is ro-tatably mounted a conventional micro-switch unit 11 comprising a box-like outer body enclosing an inner system of snap-acting contacts actuated by a pushbutton which projects through one of the sides of the said outer body (the upper side in the embodiment illustrated). This micro-switch unit 11 is submitted to the action of a torsional spring 12 mounted on the above mentioned pin 10 with one of its ends resting against a gudgeon 13 carried by the rear wall of the switch case while its other end urges upwardly a gudgeon 14 secured on the front vertical side of the micro-switch unit. On the rear side of the said unit there is mounted a small pin 15 which loosely carries a roller 16. The latter is adapted to cooperate with the lower edge of a cam member 17, as for instance made of sheet iron, which is secured onto the pusher rod 4 by a screw 8 which passes radially through the upper portion of the said cam memher, this upper portion being preferably curved longitudinally to fit on the cylindrical periphery of rod 4.

The above-mentioned cover 2 is formed with an inner boss 2a which rotatably supports a horizontal spindle 19 the inner end of which carries a spiral-shaped cam 20, while its outer end supports an adjusting knob 21 which in the embodiment illustrated is in the form of a flat circular head having a transverse actuating screw-driver slot. The said circular head is provided with a graduated scale adapted to cooperate with a mark formed on an annular rib 2b of cover 2 which surrounds the head or knob 21. A frictional washer 22 made of a resilient material such as rubber, leather or the like, is disposed between cam 20 and boss 2a both as a seal and as a braking member for the said cam 20 which is thus normally stationary.

As above indicated the actuating push-button 23 of the micro-switch unit 11 projects upwardly from the upper side of the body of the said unit and cam 20 is so disposed as to form an abutment for the said button when the micro-sw itch unit 11 is returned upwardly by the torsional spring 12.

As indicated in FIG. 3 the rear wall of the switch case 1 has a horizontal inner rib 1a adapted to form a guide for the cam member 17 which is thus retained by the said rib 1a and by the adjacent side of the micro-switch unit 11.

The apparatus described operates as follows:

At the inoperative position, i.e. when the pusher rod 4 has been fully returned to the right by its biassing spring 5, the roller 16 of the micro-switch unit is below the left .ascending portion.

end of the cam member 17 in FIG. 2, i.e. below the highermost point of the cam edge of member 17. The micro-switch unit 11 is raised by the torsional spring 12 and its push-button 23 is pressed against the stationary cam 20 and is therefore pushed inwardly with respect to the body of the micro-switch unit, the force exerted against the said button being in any case limited to the reaction of spring 12.

When the pusher rod 4 is pushed towards the left in FIGS. 1 and 2, the cam member 17 moves therewith and its lower edge engages roller 16 which is lowered against the action of spring 12. The push-button 23 is disengaged from the stationary cam 20 or, in other words, it is released by the said cam, whereby the inner contacts of the micro-switch are actuated. It will be appreciated that this actuation of the inner contacts of unit 11 occurs at a point of the inward stroke of rod 4 which is dependent on the angular position of cam 20, i.e. of the adjusting knob or head 21. Rotation of the latter thus permits of obtaining an extremely accurate adjustment of the apparatus even during operation of the latter.

The particular shape of the cam edge of member 17 may vary. In the example illustrated in FIG. 2, this member ensures operation of the microswitch unit during approximately the first half of the pusher rod stroke, the second half forming a dead residual stroke, as for instance'to take into account inertia efiects. The efiective vportion of the cam edge of the said member could also extend along the full length of the possible stroke. In some cases the cam edge could comprise, starting from the left in FIG. 2, a descending portion followed by an It will moreover be observed that this cam member 17 is easily removable and may be changed at will.

The cam member 17 may also be rotatably supported by the pusher rod 4 while being appropriately retained thereon, as for instance between suitable abutments. In this case it may be convenient to guide the said am member in such a manner that it will lower and then raise roller 16 for one direction of movement of the pusher rod 4, but will escape the said roller for the reverse direction. As to the pusher rod 4 itself, it may be prevented from rotating, if desired, by means of a slidable key provided within the blind socket 9, or by being made square or rectangular in cross-section. Its free end may carry a loose roller when required.

I claim:

1. A push-rod switch comprising a support; a pusherrod slidably carried by said support; a micro-switch unit pivotally carried by said support, said micro-switch unit embodying an actuating push-button and inner snap-acting contacts actuated by said push-button; a normally stationary but adjustable regulating abutment carried by said support to cooperate with said actuating push-button; spring means to urge said micro-switch unit towards said adjustable abutment to cause said push-button to be depressed by same with respect to said unit; cam and follower means between said pusher-rod and said microswitch unit to move said unit away from said adjustable abutment to release said push-button from the action of said adjustable abutment; said cam means comprising a member removably fixed to said pusher rod, said member having a cam edge; and a cam follower directly carried by said micro-switch unit, said cam follower being adapted to engage said cam edge under the action of said urging means.

2. A push-rod switch comprising a support; a pusherrod slidably carried by said support; a micro-switch unit pivotally carried by said support, said micro-switch unit embodying an actuating push-button and inner snap-acting contacts actuated by said push-button; a normally stationary but adjustable regulating abutment carried by said support to cooperate with said actuating push-button;

spring means to urge said micro-switch unit towards said adjustable abutment to cause said push-button to be depressed by same with respect to said unit; cam and follower means between said pusher-rod and said micro switch unit to move said unit away from said adjustable abutment to release said push-button from the action of said adjustable abutment; said adjustable regulating abutment being in the form of a spiral cam, said push-button cooperating with the outer periphery of said cam, transversely with respect to the axis of rotation of same, and said support comprising means to rotatably carry said spiral cam; frictional means to retain said spiral cam angularly; and means to manually rotate said spiral cam against the action of said frictional means.

3. A push-rod switch comprising a support; a pusherrod slidably carried by said support; a micro-switch unit pivotally carried by said support, said micro-switch unit embodying an actuating push-button and inner snap acting contacts actuated by said push-button; a normally stationary but adjustable regulating abutment carried by said support to cooperate with said actuating push-button; spring means to urge said micro-switch unit towards said adjustable abutment to cause said push-button to be depressed by same with respect to said unit; cam and follower means between said pusher-rod and said microswitch unit to move said unit away from said adjustable abutment to release said push-button from the action of said adjustable abutment; said pusher rod being cylindrical and being rotatable in .said support; said cam means embodying a member removably fixed to said pusher rod and having a cam edge, and a cam follower directly carried by said micro-switch unit to engage said cam edge under the action of said urging means; and said support comprising guiding portions to prevent rotation of said member about the axis of said pusher rod.

4. A push-rod switch comprising a switch case having an open side; a pusher rod slidably carried by said switch case in substantially parallel relation with respect to said open side; a micro-switch unit pivotally carried within said switch case, said micro-switch unit embodying an actuating push-button and inner snap-acting contacts ac tuated by said push-button; a cover to close the open side of said switch case; a spiral cam rotatably carried by said cover with its axis substantially perpendicular to said open side, said spiral cam being so disposed that its outer periphery may cooperate with the actuating push button of said micro-switch unit during oscillation of same; spring means to urge said micro-switch unit towards said spiral cam to cause said push-button to be depressed by the outer pheriphery of same with respect to said unit; cam the follower means on said pusher rod and on said microswitch unit to move said unit away from said spiral cam transversely to the axis of same to release said pushbutton from the action of said spiral cam; frictional means to retain said spiral cam angularly with respect to said cover; and means external to said cover to manual angular adjustment of said spiral cam Within said switch case against the action of said frictional means.

5. A push-rod switch comprising a support, a pusherrod slidably carried by said support; a micro-switch unit pivotally carried by said support, said micro-switch unit embodying an actuating push-button and inner snap-acting contacts actuated by said push-button; a normally stationary but adjustable regulating abutment carried by said support to cooperate with said actuating push-button; spring means to urge said micro-switch unit towards said adjustable abutment to cause said push-button to be depressed by same with respect to said unit; a cam member .removably secured to said pusher-rod to be moved therewith, said cam member having a cam edge; and a cam follower directly carried by said micro-switch unit, said cam follower being adapted to engage said cam edge to cause said unit to move away from said adjustable abutment to release said push-button from the action thereof.

6. A push-rod switch comprising a support, a pusherrod slidably carried by said support; a micro-switch unit pivotally carried by said support, said micro-switch unit embodying an actuating push-button and inner snap-acting contacts actuated by said push-button; a spiral cam having an outer periphery in cooperation with said pushbutton and an axis of rotation substantially transverse to said push-button; means on said support to rotatably carry said spiral cam; frictional means to retain said spiral cam angularly; means to manually rotate said spiral cam on said support against the action of said frictional means; spring means to urge said micro-switch unit towards said spiral cam to cause said push-button to be depressed by same with respect to said unit; a cam member removably secured to said pusher-rod to be moved therewith, said cam member having a cam edge; and a cam follower directly carried by said micro-switch unit, said cam follower being adapted to engage said cam edge to cause said unit to move away from the outer periphery of said spiral cam to release said push-button from the action thereof.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,570 Bushway Dec. 7, 1937 

